Hi, I have a 1998 GMC Jimmy, 4x4, when the weather is nice and it's above 0 Celsius out side the most I can get for mileage is 400-415 km per tank of gas, as soon as the temperature drops below 0 my mileage drops by half, no matter what i do I can't get more than 200 km per tank, I tried different grades of gas, all the spark plugs distributor and cap along with wires have been replaced, I baby drive it because the mileage is so bad at this point, it does not matter if it's city of hwy driving, it has a 65 lt tank. any suggestions. Thank you
